1. Field of the Invention
The present invention relates to a system for immobilizing two or more vertebrae relative to each other.
To be more precise, the present invention relates to a mechanical system that may be fitted by a surgeon to two or more vertebrae of the vertebral column in order to immobilize the at least two vertebrae relative to each other.
2. Description of the Prior Art
Systems of the above kind are known in the art. They comprise two pedicular screws that are screwed into the pedicles of the two vertebrae to be immobilized by an elongate member, usually referred to as a plate, whose ends are fixed to the heads of the two screws by mechanical fastening means so that the distance between the heads of the screws, and therefore the distance between the two vertebrae, remains fixed.
The screw heads are usually spherical in order to cooperate with the corresponding fastening means to form a ball-joint system allowing the plate to be fitted without applying stresses to the screws, and therefore to the vertebrae into which they are fixed, regardless of the relative direction of the two screws.
Clearly, one quality required of a system of the above kind is that the fastening of the plate and the screws should be sufficiently effective to be able to absorb the forces resulting from movements of the patient fitted with the immobilization system. Also, it is of course desirable for the system to be as easy for the surgeon to fit as possible, and for fitting it to require the shortest possible time on the operating table.
An object of the present invention is to provide a system of the type referred to above for immobilizing two or more vertebrae that constitutes a better response to the two conditions stated above.